Douglas DC-9-40

The Douglas DC-9-40 represented a further stretch of the DC-9-30, adding 1.91 meters to reach a total length of 38.28 meters and seating up to 125 passengers. Introduced in March 1968, it bridged the capacity gap between the DC-9-30 and the forthcoming DC-9-50, targeting airlines needing higher-density operations on trunk routes. The DC-9-40 retained the 28.47-meter wingspan of the -30 but required more powerful JT8D-9, -11, or -15 engines (64-71 kN) to maintain performance with the heavier fuselage. Launch customer SAS began operations in March 1968, using the type on intra-European routes. However, airlines generally preferred the more economical DC-9-30 or the higher-capacity DC-9-50, limiting demand. Only 71 DC-9-40s were built, making it one of the rarer variants. Despite modest production, the -40 proved reliable and served carriers like Toa Domestic Airlines (Japan) and Air Canada through the 1980s. It demonstrated Douglas's ability to tailor capacity to specific market needs.